Network attached storage (NAS) systems have been widely used, which are connected to hosts through a local area network (LAN), and have cluster configurations having multiple storage devices.
An example of such a storage system 200 is depicted in FIGS. 14 to 16.
FIG. 14 is a schematic diagram illustrating an example of the storage system 200. FIG. 15 is a schematic diagram illustrating paths used during normal operations in a NAS in FIG. 14, and FIG. 16 is a schematic diagram illustrating paths which cannot be tested in the NAS in FIG. 14.
The storage system 200 includes a host 201, a network storage system (NAS) 203-1 (also referred to as NAS #1 in the figure), a NAS 203-2 (NAS #2), a disk 205-1 (disk #1), and a disk 205-2 (disk #2).
The NASs 203-1 and 203-2 are information processing apparatuses that control the disks 205-1 and 205-2. The NAS 203-1 and the NAS 203-2 have similar hardware and software configurations.
The disks 205-1 and 205-2 include a redundant array of independent disks (RAID) configurations, and the disks 205-1 and 205-2 have similar hardware configurations. The disk 205-1 includes five RAID disk drives (not illustrated), and the disk 205-2 includes five RAID disk drives (not illustrated).
The NAS 203-1 and the NAS 203-2 are connected to each other through a local area network (LAN) 211, using the Ethernet®, for example.
The NAS 203-1 and the NAS 203-2 are also connected to each other through an interconnect 215, such as a Fiber Channel (FC), for example.
The NAS 203-1 and the disk 205-1 are connected to each other through a disk interface channel (I/F CH) 213-1, and the NAS 203-1 and the disk 205-2 are connected to each other through a disk interface channel 213-2, for example. The NAS 203-2 and the disk 205-1 are connected to each other through a disk interface channel 213-3, and the NAS 3-2 and the disk 205-2 are connected to each other through a disk interface channel 213-4, for example.
The disk interface channels 213-1 to 213-4 are disk interconnects, such as FCs and Serial Attached SCSIs (small computer systems interfaces) (SASs), for example.
Note that the reference symbol 203-1 or 203-2 is used hereinafter for referring to a specific NAS while reference symbol 203 is used when reference is made to any of the multiple NASs.
Note that the reference symbol 205-1 or 205-2 is used hereinafter for referring to a specific disk while reference symbol 205 is used when reference is made to any of the multiple disks.
Note that one of the reference symbols 213-1 to 213-4 is used hereinafter for referring to a specific disk interface channel while reference symbol 213 is used when reference is made to any of the multiple disk interface channels.
Here, the NAS 203-1 and the NAS 203-2 form a cluster. As used herein, the term “cluster” or “cluster configuration” refers to the configuration where the NAS 203-1, the NAS 203-2, and the disks 205-1 and 205-2 function as if they are a single device. More specifically, although the NAS 203-1 controls the disk 205-1 and the NAS 203-2 controls the disk 205-2 during normal operations, the NAS 203-1 and the NAS 203-2 can also control both of the disks 205-1 and 205-2.
Hereinafter, a set of one NAS 203 and one disk 205 may also be referred to as a cluster.
During normal operations, the NAS 203-1 and the NAS 203-2 respectively controls their own disks 205. In the case of a failure of one of the NASs 203, the other NAS 203 controls the disks 205-1 and 205-2, undertaking the function of the failed NAS 203. At that time, the redundant paths, i.e., the interface channel 213-2 or 213-3, depicted in FIG. 15 is used.
In the storage system 200, the host 201 is connected to the storage system 200 through the LAN 211. Specifically, the host 201 is connected to the NAS 203-1 and the NAS 203-2 through the LAN 211, and accesses the disks 205-1 and 205-2 controlled by the NASs 203 via the LAN 211.
In such a storage system 200, if an input/output (IO, access) from the host 201 to the disks 205 are absent, i.e., host IOs are idle, for a certain time duration, a continuity checks test is executed on each path.
For example, a continuity check on the path between the host 201 and the NASs 203 via the LAN 211 is executed by means of message communications.
A continuity check on the path between the NAS 203-1 and the NAS 203-2 via the LAN 211 is executed using the Gratuitous Address Resolution Protocol (gARP), for example.
Continuity checks on the paths between the NASs 203 and the disks 205 are executed by means of a patrol (continuity check test).
Some of the paths, however, cannot be checked in such continuity checks as described above. Such paths are indicated in FIG. 16.
For example, the logical operations of hardware or firmware upon an access of the disks 205 from the host 201 cannot be checked. For example, a test cannot be executed wherein data is written to a disk 205 from the host 201 and then the data is read to check whether the read value matches the expected value.
Further, as depicted on the right side of FIG. 16, the internal bus 207 in the NAS 203 under actual operating conditions cannot be checked in the continuity checks as described above.
Additionally, the operations of the interfaces 225, 227, 229-1, and 229-2 in the NAS 203 under actual operating conditions cannot be checked in the continuity checks.
In FIG. 16, the interface 225 is a host interface, the interface 227 is the FC interface, and interfaces 229-1 and 229-2 are disk interfaces.
Generally, for example, simple continuity checks of the internal bus 207 in the NAS 203 can be checked by accessing from the interface 225, to the interface 227 or the interface 229-1 or 229-2. However, such simple continuity checks may be insufficient, since the operation of and transfers in the internal bus 207 when the interface 225 uses the LAN may be different from those in the internal bus 207 within the NAS 203.
Further, although continuity checks under actual operating conditions are possible by accessing disks in the storage system 200 from the host 201, the resources of the host 201 are used and hence the performance of the host 201 deteriorates.
In tests that actually access to disks in the storage system 200 from the host 201, only paths that are used in normal operations are used. Hence, the redundant paths (see FIG. 15), which is one advantage of the cluster configuration, cannot be checked in continuity checks initiated by the host 201.